Did you know that you could use Consteel to perform dual analysis with 7DOF beam and/or shell elements?

Did you know that you could use Consteel to design web-tapered members?

Did you know that you could use Consteel to determine the optimum number of shear connectors for composite beams?

Did you know that you could use Consteel to determine automatically the second order moment effects for slender reinforced concrete columns?

When applying design rules in load combination filter, the most frequently used utilization type is Steel – Dominant results. What results are exactly considered by this option and what do corresponding limitations mean?

Introduction

There are four ways to apply load combination filter: based on limit states and load cases, manually, and by rules. Unlike the other three methods, filter by rules is only possible based on analysis and/or design results.

The most effective way to reduce the number of load combinations is definitely the use of design rules.

With design rules, load combinations can be selected based on utility ratios. Utilizations are available from several design checks, including dominant results and detailed verifications for steel elements, such as general elastic cross-section check, pure resistances, interactions, and global stability.

The meaning of the dominant check

The dominant check is not always the check which gives the maximal ratio but the one with the maximum RELEVANT ratio. Typical example: if plastic interaction formulas are valid, those results will be dominant over general elastic cross-section check results, although the latter are higher.

Steel – Dominant results

Steel – Dominant results option contains the utility ratio of the dominant check at every finite element node, in all load combinations. Meaning that there are as many utilization values as the number of load combinations calculated, in every FE node.

It is also important to understand the difference between the utilizations of Maximum of dominant results and Steel -Dominant results. Maximum of dominant results option contains the dominant utility ratio of the dominant load combination at every node, like an envelope of Steel-Dominant results. Meaning there is only one utilization value in every FE node. Also, it is the same as the dominant result table on Global checks tab.

When a rule is applied, the utilizations of the chosen utilization type are compared against the limitation. The load combinations which give the results that correspond to the limitation, are selected by the rule. Every FE node of the selected model portion is examined.

Limitations in case of Steel – Dominant results

• Maximum: to select the combinations which cause the maximum utilization at any node. It can be the same as Maximum of dominant results, except if there are combinations where the utilization is the same and it is maximal. In this case, here all the combinations are selected, while with Maximum of dominant results, there is always one maximum.
• More than % of maximum: to select the combinations as in ’Maximum’ plus those which cause utilization that is more than the given percentage of the maximum. E.g. at a certain point max utility ratio is 80%, Limitation= More than 90% of maximum. This rule will select all the load combinations which cause utility ratios between 0,9*80=72% and 80%.
• More than: to select the combinations which cause utilization more than the defined value at any point.

Let’s see an example of a simple 2D frame for better explanation. Right-side beam is in the portion for which three design rules were applied. Five points are selected for representation but of course all the nodes of the portion are examined against the rules’ limitations.

The utilizations of the five dedicated FE node in all 11 load combinations are shown on the below diagram. (To find all of these utilizations in the attached model, global checks must be calculated for the load combinations one-by-one.)

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Introduction

In ConSteel, there are three options for designing reinforced concrete columns: the Manual Nominal Curvature Method, the Automatic Nominal Curvature Method, and the Nominal Stiffness Method.

Each method has its advantages and disadvantages and should be used in different situations. We will now briefly review these methods and show how they can be used. Example models and a flowchart guide is also available at the end of the overview.

You can find the related chapters within the Online Manual about how to access these features in the Structural design and Structural modeling chapters.

Summary table

The following table summarizes the most important information about the three methods. Click on the table to see it in full screen.

We will now illustrate the application of these methods with a few short examples.

Examples

Manual Nominal Curvature Method

Create section

Define structure without imperfections

Define reinforcement

Define design parameters

First order analysis

Design

Automatic Nominal Curvature Method

Only the steps presented, which are different from the Manual Nominal Curvature Method.

Imperfections

Design parameters

First order analysis – with imperfections

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Did you know that you could use Consteel to design a hot-rolled crane beam considering the effect of code-prescribed load eccentricities?

In Consteel 16, we introduced the function of load combination filter. Filtering is possible based on the load combinations’ limit state, load cases, and corresponding analysis and design results. The goal is to create different sets for the different steps of the optimization and reduce calculation time while making sure that all the relevant load combinations are considered. Let’s see what a conscious design workflow looks like in practice!

Description

It is a significant problem in almost all structural design projects that the standards define many possible load cases and combinations to evaluate. Although most of these load combinations are never relevant or provide decisive design situations, it is usually not evident which ones might be neglected safely, especially when considering, that different load combinations can be relevant for different parts of the structure, like primary or secondary structure, connections, etc. Accordingly, the optimization process is overloaded by a large amount of unnecessary calculations.

With the load combination filter function, a reduced list of load combinations aka a load combination set can be created and saved for the different steps of the optimization.

The optimal workflow for the filter may vary for the different purposes the sets are created for, but there is a recommended general process that can serve as the basis for all of them. First, run the simplest calculations and use the results for a rough selection which will already decrease the number of load combinations noticeably.  Then one can increase the complexity of the calculations and further reduce the list of combinations by using stricter filters. If needed, this step can be repeated. This iterative process allows us to avoid complex and time-consuming calculations for all the thousands of load combinations.

1 – all load combination, no filter;
2 – initial set with broad filter;
3 – working set with strict filter

Detailed process

Modeling

The base of all optimization processes is a correctly built structural model. So, the first step is geometrical and structural modeling and load definition. It is advisable to run a first-order analysis for only one or two load cases and diagnostics to find possible modeling errors. Load combinations can be created after that. Every limit state that will be used during the whole design of the structure, should be defined. Consteel’s automatic load combination generation function is an efficient tool to do it.

Calculation and filter

On the Load combination set definition dialog, it is possible to create load combination sets by selecting the combinations based on their limit state and/or the load cases they contain. But usually, filtering on specific analysis or design results will likely be more effective in reducing the number of combinations. Using the above-described general workflow, the steps are as follows:

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Introduction

It is essential for the effective work of the design engineers to have a model which is easy to overview. In Consteel there are several functions to achieve that such as layers and portions, and also Member coloring by cross-section.

How it works

The color of the displayed objects is now determined by the object style settings in Options.

Layer color can overwrite these settings if the Layer style cell is checked on Layers dialog.

In the case of beam type members, it is also possible to set the color of the object according to the section it has defined. Coloring by member can be set with Object color setting dialog in the right bottom corner:

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Introduction

As it is important to have a clear overview of the structural model, the visualization of the analysis results is also essential when it comes to effective design process. From Consteel 15 we use an advanced method for deformation representation which makes it smooth and realistic.

Description

Civil engineering software in general use the traditional beam-type deformation representation where the section is shown on the deformation of the reference line. There are some consequences of this representation mode that can be disturbing for the users. The best example is an eccentric support, where the deformed shape is visualized as if the supported point would’ve moved. The reference line indeed moved but the supported point not – the representation can not show that.

With Consteel’s advanced deformation representation not only the position of the reference line points are calculated and the section is only shown automatically, but the positions of all the decorated points of the section are calculated during a post-process and so it is possible to represent the real deformations. As a consequence it is also visible that the supported points stay in position.

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